Cytotoxic changes in hair cells secondary to pneumococcal middle-ear infection

To determine whether the bacterial toxins associated with otitis media coul d induce morphologic changes in the organ of Corti, we inoculated the middl e-ear cavities of healthy guinea pigs with either Streptococcus pneumoniae or sterile saline and then examined the organ of Corti histologically at 1, 2, and 3 weeks postinoculation. We found that the outer hair cells (OHCs) in the infected ears underwent several changes that were dependent on both the length of time following inoculation and also the position of the OHCs in the cochlea. At 2 weeks postinoculation, 7.0 to 20% of the OHC nuclei fr om the infected animals became very swollen, with the most significant swel ling occurring in the basal turn. At 3 weeks postinoculation, 2.5 to 3.5% o f the OHCs were missing in the infected animals, with the most significant loss occurring in the basal and middle turns. These results suggest that ba cterial otitis media can produce cytotoxic changes in the cochlea. These ch anges may be a clinically significant factor in the temporary and permanent sensorineural hearing loss that has been associated with bacterial otitis media.